Method for operating two-cycle engines



Lawrence E. Riemenschneider, Chelsea, Mich.

N Drawing. Application Augusti8, 1955 7 Serial No. 527,163 n i 2 Claims.onizer-1 The present invention relates to lubricant motor fuels fortwo-cycle engines and lubricant additives useful in the production ofsuch fuels.

Inthe operation of gas engines of the two-cycle type, the lubricatingoil is mixed directly with the gasolene or other fuel, as distinguishedfrom other types of gas engines in which the lubricating oil is retainedin the crankcase. The mixture consisting of gasolene and a minorproportion of lubricating oil is fed to the combustion chamber, where itis burned. However, the design and carburetion adjustment of thetwo-cycle engine is necessarily directed toward obtaining the greatestefficiency and maximum horsepower from the gasolene proper, since thebest performance of the engine is obviously dependent upon propercombustion of the component which forms by far the greatest part ofthefuel mixture. Thus, the lubricant must burn as best it can; and in thecase of lubricants known heretofore, faulty combustionof the lubricantcomponent of the fuel mixture has led to a great deal of difiiculty.

In particular, faulty combustion of the lubricant component of the fuelmixture has heretofore resulted in carbon and sludge deposits whichinterfere with the exhaust port and cause fouling ofthe sparkplugs andsticking of the rings.Moreover, excessive carbon deposits have tended tobuild up on the head of the piston and in the cylinder head and ringgrooves. These difficulties have led to marked reduction in powerdelivery and have required frequent disassembly and cleaning of thetwo-cycle engine. With a new, clean engine, no more than thirty hours ofoperation before cleaning could heretofore be expected; and uponsubsequent operation, the time between plug cleaning has dropped to afraction of this number of hours and in some cases has fallen to lessthan one hour.

Apart from the reduction in power and necessity'for frequent cleaningresulting from such deposits, a further difficulty has arisen apart fromoperation of the engine and as a result of mere storage of the enginecontaining fuel mixtures known to the prior art. This difficulty hasmanifested itself in the form of gummy deposits forming a coating onmetal parts commonly known in the art as varnish.

Although many attempts Were made to overcome the foregoing difficultiesand other disadvantages, none, so

far as I am aware, was entirely successful when carried into practicecommercially on an industrial scale.

Accordingly, it is an object of my invention to provide a lubricantmotor fuel for two-cycle engines, which will leave no appreciableresidue upon combustion.

A further object of the invention is the provision of a lubricatingadditive for mixture with two-cycle engine fuel, such that the entiremixture will vaporize or burn without leaving an appreciable deposit onthe engine parts. i

A still further object of my invention is the provision of a lubricatingfuel for two-cycle engines, which will rates Patent U 2,896,593 PatentedJuly 28, 1959 2 permit storage of the engine with greatly reduced gumformation.

Other objects and advantages of the present invention will becomeapparent from the following description and examples.

The lubricating oil component of my invention consists of polymersofolefins of which the monomers have not more than five carbon atoms.Among the operative embodiments are polymers of ethylene, propylene,butylene, isobutylene, and amyline; and particularly preferred isisobutylene. Polymerization of these mono nrgr s to the extent necessaryto produce a lubricating oil 'may be carried out according to the methodof any of US. Patents Numbers 2,278,445, April 7, 1942, 2,301,052November 3, 1942, 2,318,719, May 11, 1943, 2,329,714, September 21,1943, 2,345,574, April 4 1944, or 2,422,443, June 17, 1947. Although theoperative embodiments of monomers are selected from the lower ethyleneseries, it will of course be understood that tiny amounts of polymersformed from higher monomers will not seriously affect the operativenessofthe invention.

Temperatures up to aboutSOO degree Fahrenheit are encountered adjacentthe crankcase and cylinder walls of two-cycle engines; and the polymersof the lower ethylene series described above will remain stable somewhatbeyond that temperature range. However, the polymers according to theinvention will depolymerize to a gaseous state at around 625 degreesFahrenheit. Inasmuch as the temperatures reached during combustion ofthe fuel mixture are substantially above this latter temperature, it isobvious that the polymer components of the mixture will retain theirlubricatingfunction until combustion and willthen completelydepolymerize, leaving no residue. Thus, it does not matter that thepolymeric lubricant component of the fuel mixture does not burncompletely in the combustion chamber, since the unburned portiondepolymerizes at the combustion temperatures and is completely exhaustedas the monomeric gas from which the polymeric component was initiallyformed.

Fuel mixtures according to my invention are formed by the thoroughmechanical mixing of a small proportion of polymeric lubricant additiveaccording to the. invention with a liquid fuel such as gasolene ornaptha. The two components are mutually miscible. A preferred proportionof polymeric lubricant additive is 6% by volume of the whole. Asubstantially smaller proportion of lubricant additive gives a decreasedlubrication effeet; and higher proportions are not only wasteful butalso decrease the efficiency of performance. However, when the two-cycleengine is new and in being broken in," it may be desirable to use asomewhat richer mixture including polymeric lubricant additive in theamount of about 9% by volume of the whole.

Although the use of polymeric lubricant additives in fuel mixturesaccording to my invention greatly reduces the amount of harmful depositwhen used with a gasolene of any type, it was nevertheless found thatsome of the deposit was due to the use of generally available gasolenescontaining lead and produced by the so-called cracking processes. Thesegasolenes produced by cracking contain a relatively high proportion ofunstable molecules known to the art as wild molecules which combine withmetals and other substances to form varnishes and gums. Moreover,certain components of the residues left by these commonly availablegasolenes are electrically conductive at the temperatures encountered inthe combustion chamber of a two-cycle engine, although the depositswould be virtually harmless in a four-cycle engine. Heretofore, theharmful effect of the residues left by the commonly available gasolenescontaining lead and produced by cracking processes had been completelymasked by the greater residues left by lubricant additives heretoforeused.

Thus, it was found desirable also to provide the further refinement ofthe compositionof fuel mixtures according to my invention, comprisingthe use of lead-freestraight run gas olenes as the major component ofthe fuel. By straight run'gasolene is meant the natural cat which isobtained from crude oil by ordinary distillation before the remainingcrude oil is subjected to cracking for the production of crackedgasolene. Thus, straight run gasolene is sharply distinguished fromcracked gasolene, which latter has by contrast a relatively highproportion of wild molecules,

For the purpose of enabling those skilled in the art to practice theinvention, the following exemplary illustration is given:

As a lubricant additive, a polymer of isobutylene was selected, having apour point of minus 20 degrees Fahrenheit, a flash point of 215 degreesFahrenheit, a'

viscosity at 100 degrees Fahrenheit of 230 Saybolt seconds and aviscosity at 210 degrees Fahrenheit of 50 Saybolt seconds, and aviscosity index of 114. This additive was mixed inthe amount of 6% byvolume of the whole with a'straight run gasolene known as stove andlighting napth-a having a lead content of 0, an octane number of 65, asulphur content of 0.02%, an A.P.-I. gravity of 64.5 degrees, and'aboiling point range'initially at 109 degrees Fahrenheit, 10% at 156degrees Fahrenheit, at 169 degrees Fahrenheit, at 192 degreesFahrenheit, at 206 degrees Fahrenheit, at 216 degrees Fahrenheit, at 231degrees Fahrenheit, at 245 degreesFahrenheit, at .265 degreesFahrenheit, at 294 degrees Fahrenheit, and an end boiling point at 339degrees Fahrenheit. The mixture was borned as fuel in a two cycleengine; and after 48 hours of operation, no appreciable depositofresidue was noticed in the exhaust port, on the piston'head, in thecylinder head, or in the ring groove. Without removal of the fuel fromthe engine, the engine was permitted to stand for a month; and after theexpiration ofthis'l'atter time, no appreciable deposit of varnish or gumwas noticed on any'of the parts. f

Thus, from a consideration of the foregoing disclosure,

4 it will be obvious that I have achieved all of the initially recitedobjects of my invention.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

I claim:

1. A method of avoiding carbon and sludge residues on the parts of atwo-cycle engine upon combustion and of reducing gum formation on theengine parts during storage of a two-cycle engine, which comprisesoperating a said two-cycle engine on a fuel consisting essentially of amixture of lead-free, straight run gasolene, and a small but effectiveamount, from about 6% to about 9% by volume of the whole, of polymers ofolefins of which the monomers have not more than .five carbon atoms.

2. A method of, avoiding carbon and sludge residues on the parts of atwo-cycle'engine upon combustion and of reducing gum formation on theengine parts during storage of a two-cycle engine, whichcomprises'operating a said two-cycle engine on a fuel consistingessentially of a mixture of lead-free, straight run gasolene, and asmall but effective amount, from about 6% to about 9% by volume of thewhole, of polymers of isobutylene.

References Cited in the file of this patent UNITED STATES PATENTS GreatBritain Oct. 4., 1933'

